1. Field of the Invention
The present invention relates to soybean protein hydrolysates, their production and use.
2. Description of the Prior Art
As consumers want to avoid use of synthetic food additives, recently, it has been strongly desired to develop substitutes derived from natural products for synthetic food additives, for example, synthetic emulsifying agents and whipping agents. In this respect, soybean protein has been studied heretofore as a natural product for the raw material of substitutes for synthetic emulsifying agents and whipping agents. For example, JP-A 56-26171, JP-A 57-16674 and JP-A 6-197788 disclose enzymatic decomposition of soybean protein under specific conditions to obtain polypeptides to be used mainly as substitutes for synthetic emulsifying agents. In addition, from the viewpoint of soybean protein components, to utilize glycinin acidic subunit (JP-A 63-36748) or glycinin basic subunit has been known. JP-A 49-109551, JP-A 53-58982, JP-A 58-36347, JP-A 60-176549, JP-A 60-184372, JP-A 61-216646 and JP-A 4-311354 disclose enzymatic decomposition of soybean protein under specific conditions to obtain polypeptides to be used mainly as substitutes for synthetic whipping agents.
Further, U.S. Pat. No. 2,502,482 and U.S. Pat. No. 3,814,816 disclose decomposition of acid precipitated soybean protein with pepsin to a specific decomposition degree or more, and to use a supernatant obtained by fractionating polypeptides resulted from enzymatic decomposition of acid precipitated soybean protein with pepsin as a whipping agent. U.S. Pat. No. 4,409,248 discloses fractionation of 7S component of soybean protein and decomposition of the fractionated 7S component with an enzyme to use the resultant polypeptides as a whipping agent. U.S. Pat. No. 4,370,267 discloses fractionation of 11S component of soybean protein and decomposition of the fractionated 11S component with pepsin to use the resultant polypeptides as a whipping agent. Furthermore, U.S. Pat. No. 4,632,903 discloses production of an egg white substitute by two stage decomposition with a microbial enzyme at a neutral pH range.
However, for decomposition of a specific fraction of soybean protein, these known techniques require very complicated steps because the desired specific fraction should be separated beforehand by adjusting pH and salt concentration and then decomposing it. In addition, when additional fractionation is required after decomposition, the problem is lowering of yields of desired polypeptides. Then, it is difficult to obtain polypeptides having both excellent emulsifying and whipping capabilities in a good yield.
The present assignee's EP-A 0 797 927 (corresponding to co-pending U.S. patent application Ser. No. 08/828,939) discloses a soy protein hydrolysate with a low content of .beta.-conglycinin obtained by selective decomposition of .beta.-conglycinin and food products comprising the hydrolysate. The present assignee's EP-A 0 797 928 (corresponding to co-pending U.S. patent application Ser. No. 08/828,393) discloses selective hydrolysis of a specific constituent polypeptide of soybean protein, e.g., glycinin or .beta.conglycinin.
An object of the present invention is to provide a polypeptide composition having both excellent emulsifying and whipping capabilities which can be utilized in various technical fields including food, beverages, cosmetics, toiletries, medicines, and industrial application.
Another object of the present invention is to provide a process for producing the polypeptide composition.
Still another object of the present invention is to provide a food additive utilizing the polypeptide composition and a food product utilizing the food additive.
These objects as well as other objects and advantages of the present invention will become apparent to those skilled in the art from the following description with reference to the accompanying drawings.